Possible Feature: Setting to control RX gain

[kj5o]

Two of the things I really like about OpenGD77 on my GD77 are the RSSI display and the fine-tune relative TX power setting, because these are both useful for foxhunting. (The TX power is good for getting a good local range for the fox transmitter in a relatively small search area.)

I don't know much about the internals of the radio, but I understand there is a microcontroller (which runs opengd77) that communicates with a transceiver module to do the actual RF functions. Does the radio module permit changing the receiver gain values? If so, could there be a feature to basically reduce the RX gain on the radio, thereby letting the radio have a built-in step attenuator? Even a "regular" vs "low gain" would be good, not necessarily having multiple step values. This could make the GD-77 a killer foxhunt receiver.

[VK3KYY]

Two of the things I really like about OpenGD77 on my GD77 are the RSSI display and the fine-tune relative TX power setting, because these are both useful for foxhunting. (The TX power is good for getting a good local range for the fox transmitter in a relatively small search area.)

I don't know much about the internals of the radio, but I understand there is a microcontroller (which runs opengd77) that communicates with a transceiver module to do the actual RF functions. Does the radio module permit changing the receiver gain values? If so, could there be a feature to basically reduce the RX gain on the radio, thereby letting the radio have a built-in step attenuator? Even a "regular" vs "low gain" would be good, not necessarily having multiple step values. This could make the GD-77 a killer foxhunt receiver.

The radios use the AT1846S RF Chip, which does not have any control of RF gain.

If you search around there are data sheets for this chip on the web, even though in theory its not supposed to be publically available.

About the only thing that could be done would be to turn off the RF preamp, but this would make the radio almost completely insensitive, and you may as well remove the antenna as you'd probably get a similar result.

[kj5o]

Well.. Depending on how insensitive, that might be just the ticket. If there is a directional-gain antenna attached, but the signal is S9+20dB with the preamp on, would the receiver still be getting enough signal through the antenna port to even get something in the range of S1 to S5? Or would most of the signal be bleeding in through the case, making the directionality of the antenna moot?

[AA3RP]

Jumping in here.

In the Fox Hunt I am assuming you are using something like a 2 or 3 element yagi as your antenna. If so when the RSSI goes full scale you could add an inline attenuator, Say 6db or so.

Not near as nice as having a radio that can adjust the pre-amp dynamically but practical and doable.

You may have thought of this already, and if so, just call me slow to the party

all the best
AA3RP

[VK3KYY]

I will need to test what happens when the preamp is turned off. Most likely this will vary depending on which type of radio is being used e.g GD77 or UV380 or MD9600

From what I recall turning on the wrong preamp e.g. UHF for 145MHz causes less amplification, but again , most likely this would vary from radio to radio model

[kj5o]

In the Fox Hunt I am assuming you are using something like a 2 or 3 element yagi as your antenna. If so when the RSSI goes full scale you could add an inline attenuator, Say 6db or so.

Not near as nice as having a radio that can adjust the pre-amp dynamically but practical and doable.

Yes, that is rather the point -- to not have to carry around an attenuator, if the radio can be made to do the equivalent by software control.